netty5/microbench
Nick Hill 35161ad174 Further reduce ensureAccessible() overhead (#8895)
Motivation:

This PR fixes some non-negligible overhead discovered in the ByteBuf
accessibility (non-zero refcount) checking. The cause turned out to be
mostly twofold:
- Unnecessary operations used to calculate the refcount from the "raw"
encoded int field value
- Call stack depths exceeding the default limit for inlining, in some
places (CompositeByteBuf in particular)

It's a follow-on from #8882 which uses the maxCapacity field for a
simpler non-negative check. The performance gap between these two
variants appears to be _mostly_ closed, but there's one exception which
may warrant further analysis.

Modifications:

- Replace ABB.internalRefCount() with ByteBuf.isAccessible(), the
default still checks for non-zero refCnt()
- Just test for parity of raw refCnt instead of converting to "real",
with fast-path for specific small values
- Make sure isAccessible() is delegated by derived/wrapper ByteBufs
- Use existing freed flag in CompositeByteBuf for faster isAccessible()
- Manually inline some calls in methods like CompositeByteBuf.setLong()
and AbstractReferenceCountedByteBuf.isAccessible() to reduce stack
depths (to ensure default inlining limit isn't hit)
- Add ByteBufAccessBenchmark which is an extension of
UnsafeByteBufBenchmark (maybe latter could now be removed)

Results:

Before:

Benchmark   (bufferType)  (checkAccessible)  (checkBounds)   Mode  Cnt
Score          Error  Units
readBatch         UNSAFE               true           true  thrpt   30
84524972.863 ±   518338.811  ops/s
readBatch   UNSAFE_SLICE               true           true  thrpt   30
38608795.037 ±   298176.974  ops/s
readBatch           HEAP               true           true  thrpt   30
80003697.649 ±   974674.119  ops/s
readBatch      COMPOSITE               true           true  thrpt   30
18495554.788 ±   108075.023  ops/s
setGetLong        UNSAFE               true           true  thrpt   30
247069881.578 ± 10839162.593  ops/s
setGetLong  UNSAFE_SLICE               true           true  thrpt   30
196355905.206 ±  1802420.990  ops/s
setGetLong          HEAP               true           true  thrpt   30
245686644.713 ± 11769311.527  ops/s
setGetLong     COMPOSITE               true           true  thrpt   30
83170940.687 ±   657524.123  ops/s
setLong           UNSAFE               true           true  thrpt   30
278940253.918 ±  1807265.259  ops/s
setLong     UNSAFE_SLICE               true           true  thrpt   30
202556738.764 ± 11887973.563  ops/s
setLong             HEAP               true           true  thrpt   30
280045958.053 ±  2719583.400  ops/s
setLong        COMPOSITE               true           true  thrpt   30
121299806.002 ±  2155084.707  ops/s


After:

Benchmark   (bufferType)  (checkAccessible)  (checkBounds)   Mode  Cnt
Score          Error  Units
readBatch         UNSAFE               true           true  thrpt   30
101641801.035 ±  3950050.059  ops/s
readBatch   UNSAFE_SLICE               true           true  thrpt   30
84395902.846 ±  4339579.057  ops/s
readBatch           HEAP               true           true  thrpt   30
100179060.207 ±  3222487.287  ops/s
readBatch      COMPOSITE               true           true  thrpt   30
42288494.472 ±   294919.633  ops/s
setGetLong        UNSAFE               true           true  thrpt   30
304530755.027 ±  6574163.899  ops/s
setGetLong  UNSAFE_SLICE               true           true  thrpt   30
212028547.645 ± 14277828.768  ops/s
setGetLong          HEAP               true           true  thrpt   30
309335422.609 ±  2272150.415  ops/s
setGetLong     COMPOSITE               true           true  thrpt   30
160383609.236 ±   966484.033  ops/s
setLong           UNSAFE               true           true  thrpt   30
298055969.747 ±  7437449.627  ops/s
setLong     UNSAFE_SLICE               true           true  thrpt   30
223784178.650 ±  9869750.095  ops/s
setLong             HEAP               true           true  thrpt   30
302543263.328 ±  8140104.706  ops/s
setLong        COMPOSITE               true           true  thrpt   30
157083673.285 ±  3528779.522  ops/s

There's also a similar knock-on improvement to other benchmarks (e.g.
HPACK encoding/decoding) as shown in #8882.

For sanity I did a final comparison of the "fast path" tweak using one
of the HPACK benchmarks:

(rawCnt & 1) == 0:

Benchmark                     (limitToAscii)  (sensitive)  (size)   Mode
Cnt      Score     Error  Units
HpackDecoderBenchmark.decode            true         true  MEDIUM  thrpt
30  50914.479 ± 940.114  ops/s


rawCnt == 2 || rawCnt == 4 || rawCnt == 6 || rawCnt == 8 ||  (rawCnt &
1) == 0:

Benchmark                     (limitToAscii)  (sensitive)  (size)   Mode
Cnt      Score      Error  Units
HpackDecoderBenchmark.decode            true         true  MEDIUM  thrpt
30  60036.425 ± 1478.196  ops/s
2019-02-28 20:41:16 +01:00
..
src/main Further reduce ensureAccessible() overhead (#8895) 2019-02-28 20:41:16 +01:00
pom.xml Adding an execute burst cost benchmark for Netty executors (#8594) 2018-12-04 15:46:48 +01:00
README.md Fix wiki link 2014-02-14 12:04:12 -08:00

Microbenchmark tests

See our wiki page.